Bulk polymerization process for preparing high solids and uniform copolymers

Abstract

A process to continuously bulk polymerize acrylic monomers to prepare low molecular weight, uniform, polymers employs minor amounts of initiator and, optionally solvents, at short residence times and moderate reaction temperatures to provide high yields of a product suitable for high solids applications.

What I claim is: 
     
       1. A continuous bulk polymerization process for preparing enhanced yields of high solids, non-styrenic acrylic polymer product having a number average molecular weight of about 1000 to 2500 a polydispersity ratio of less than about 3; a dispersion index of up to about 5 and a low chromophore content comprising the steps of continuously: (a) charging into a continuous mixed reactor zone containing a molten resin mixture consisting esentially of; (i) at least one acrylic monomer;   (ii) a polymerization initiator in amounts to provide a molar ratio of said initiator to said acrylic monomer from about 0.0005:1 to 0.06:1,   (iii) from about 0 to 25 percent based on the weight of acrylic monomers of a reaction solvent, wherein said molten resin mixture comprises unreacted acrylic monomers and the acrylic polymer product;     (b) maintaining a flow rate through said reaction zone sufficient to: (i) provide a residence time of said charged acrylic monomer in said reaction zone of from about 1-30 minutes; and   (ii) maintain a predetermined level of reaction mixture in said reaction zone, and;     (c) maintaining the molten resin mixture at an elevated temperature with the range of from about 180° C. to 270° C. sufficient to provide accelerated conversation to a readily processable, uniform, concentrated polymer product.   
     
     
       2. The process of claim 1 wherein the temperature is within the range from about 215° C. to 260° C. 
     
     
       3. The process of claim 1 wherein at least two acrylic monomers are charged into the reactor zone. 
     
     
       4. The process of claim 1 including the step of separating the polymer product from unreacted monomers and by-products of the reaction. 
     
     
       5. The process of claim 1 in which the initiator has a half-life of about 10 hours at 100° C. 
     
     
       6. The process of claim 5 in which the initiator is a peroxide or hydroperoxide. 
     
     
       7. The process of claim 1 in which the initiator is employed in a mole ratio from about 0.005:1 to 0.04:1. 
     
     
       8. The process of claim 1 in which the initiator is employed in a mole ratio from about 0.005:1 to 0.015:1. 
     
     
       9. The process of claim 1 in which the solvent is selected from a higher boiling (i) aromatic alcohol, (ii) an alcohol or glycol ether, ester, mixed ether and mixed ester, (iii) a (poly)alkylene glycol dialkyl ether, and (iv) a hydrocarbon fraction. 
     
     
       10. The process of claim 4 in which the residence time is from about 1 to 20 minutes. 
     
     
       11. The process of claim 3 wherein the acrylic monomers include about 50-90% by weight of a non-functional acrylic monomer and about 5-50% by weight of a functional acrylic monomer. 
     
     
       12. The process of claim 11 wherein the monomer charge is adapted to form a crosslinkable theremoset polymer which comprises 60-90% by weight of an alkyl ester of acrylic or methacrylic acid and 10-40% by weight of a hydroxy alkyl acrylate or hydroxy alkyl methacrylate. 
     
     
       13. The process of claim 12 wherein the functional acrylic monomer is selected from the group consisting of hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropylacrylate, hydroxypropyl methacrylate, hydroxyhexyl acrylate, hydroxyhexyl methacrylate and mixtures thereof.